Production from wells in the oil and gas industry often contain particulates such as sand. These particulates could be part of the formation from which the hydrocarbon is being produced, introduced particulates from hydraulic fracturing or fluid loss material from drilling mud or fracturing fluids or from a phase change of produced hydrocarbons caused by changing conditions at the wellbore (Asphalt or wax formation). As the particulates are produced, problems occur due to abrasion, and plugging of production equipment. In a typical startup after stimulating a well by fracturing, the stimulated well may produce sand until the well has stabilized, often up to a month after production commences. Other wells may require extended use of the desander 10.
In the case of gas wells, fluid velocities can be high enough that the erosion of the production equipment is severe enough to cause catastrophic failure. High fluid stream velocities are typical and are even purposefully designed for elutriating particles up the well and to the surface. An erosive failure of this nature can become a serious safety and environmental issue for the well operator. A failure such as a breach of high pressure piping or equipment releases uncontrolled high velocity flow of fluid which is hazardous to service personnel. Release to the environment is damaging to the environment resulting in expensive cleanup and loss of production. Repair costs are also high.
In all cases, retention of particulates contaminates both surface equipment and the produced fluids and impairs the normal operation of the oil and gas gathering systems and process facilities.
In one prior art system, a pressurized tank (“P-Tank”) is placed on the wellsite and the well is allowed to produce fluid and particulates. The fluid stream is produced from a wellhead and into a P-Tank until sand production ceases. The large size of the P-Tank usually restricts the maximum operating pressure of the vessel to something in the order of 1,000–2,100 kPa. In the case of a gas well, this requires some pressure control to be placed on the well to protect the P-Tank. Further, for a gas well, a pressure reduction usually is associated with an increase in gas velocity which in turn makes sand-laden wellhead effluent much more abrasive. Another problem associated with this type of desanding technique is that it is only a temporary solution. If the well continues to make sand, the solution becomes prohibitively expensive. In most situations with this kind of temporary solution, the gas vapors are not conserved and sold as a commercial product.
An alternate known prior art system includes employing filters to remove particulates. A common design is to have a number of fiber-mesh filter bags placed inside a pressure vessel. The density of the filter bag fiber-mesh is matched to the anticipated size of the particulates. Filter bags are generally not effective in the removal of particulates in a multiphase conditions. Usually multiphase flow in the oil and gas operations is unstable. Large slugs of fluid followed by a gas mist is common. In these cases, the fiber bags become a cause a pressure drop and often fail due to the liquid flow therethrough. Due to the high chance of failure, filter bags may not be trusted to remove particulates in critical applications or where the flow parameters of a well are unknown. An additional problem with filter bags in most jurisdictions is the cost associated with disposal. The fiber-mesh filter bags are considered to be contaminated with hydrocarbons and must be disposed of in accordance to local environmental regulation.
Clearly there is a need for more versatile and cost effective system of particulate handling.